I have both, here's the difference. Magneto engines require learning the technique to hand start. Prop position is most important. Electronic ignition is not so picky. Most people will not take the time to learn the starting technique for a magneto engine and use a starter. My
g-62 will start in three flips just like the EI engines if it is properly primed. I can flip start most magneto engines using the same technique.
Magneto engines are heavier, but when you add in the extra weight of the batteries and wiring EI engines lose some of their advantage.
EI engines idle slightly smoother but power is exactly the same. I fly warbirds and almost always need the nose weight so there is an advantage to using the magneto engine. The logic of endless worry about the weight of the engine and then having to add nose weight to balance escapes me. Magneto engines are cheaper. I don't worry about rf and the placement of the radio nearly as much with magneto engines. No extra parts to go bad like batteries and switches. I guess it boils down to the argument of simplicity vs newer technology.
Of course I am comparing the same engine with or without EI, Not a G-38 against a DA-50.

Larry